We shall study how toxic lipopolysaccharide (LPS) activates macrophages and B cells. For this study, we shall use the petaacyl diphosphoryl lipid A derived from the nontoxic lipopolysaccharide of Rhodobacter sphaeroides (Rs-DPLA) as the competitive inhibitor of the action of a highly purified and toxic deep rough chemotype LPS of Escherichia coli D31m4 (Re-LPS). We shall study the effect of Rs-DPLA (and its analogs) on: (a) binding of toxic LPS to macrophages (using [14C]-labeled Ra-LPS from E. coli); (b) the appearance of early LPS-inducible genes and protein tyrosine phosphorylation; (c) activation of NF-kappaB and Oct-2 in 7OZ/3 pre-B cells. From these studies, we hope to elucidate the mechanism of activation of the immune cells by toxic LPS which triggers the shock syndrome. We shall attempt to develop a novel multiple drug therapy for the prevention of Gram-negative septic shock which is a life-threatening medical problem associated with high mortality. The major component in this therapy will be Rs-DPLA. It is a potent antagonist of toxic LPS (i.e., against the Re-LPS) and induces corticosteroids in vivo. Thus, we shall prevent the induction of the two important mediators of septic shock, TNF-alpha and IL-1beta, with Rs-DPLA, and at a later stage of sepsis neutralize or control the level of another well-known mediator of shock, IFN-gamma, by the use of either anti-IFN-gamma antibody or cyclosporin A. Antibiotics and other drugs will also be tested in combination with those listed above. The murine galactosamine-sensitized and the cecal ligation and puncture shock models will be used for this study. We shall also study how Rs-DPLA/Re-LPS induces corticosteroids in vivo, which probably involves the hypothalamic-pituitary-adrenal axis. Rs-DPLA might become one of the important component in the development of an effective multiple-drug therapy for the prevention of mitigation of septic shock.